Reproduction steps (you might not need all of them, haven’t been spending too much time with this):
- Create parent Actor (note: this is a simple actor, parent is only the name right now).
- Parent viewport should contain 2 static meshes. Static mesh 1 as scene root with no mesh set. Static mesh 2 as child of static mesh 1. Static mesh 2 should be something visible.
- Create child1 Actor as child-Blueprint of parent. Change the the visual for static mesh 2 for child1.
- Create child2 Actor as child-Blueprint of parent.
- Add child1 to the viewport of child2 as child of static mesh 1.
- Re-compile all 3 blueprints. All 3 thumbnails will now contain the visual of child1. Any other child-Actors of parent will as well.
Some other thumnails that have nothing to do with this parent-child combination (and this seems to be arbitrary) are changed as well. This is really confusing and and slows you down a lot.
This does NOT affect the ingame visuals. Neither for in editor play nor for the packaged version (at least for me).